ES2267629T3 - PROCEDURE AND APPARATUS FOR THE CONTINUOUS PRODUCTION OF PLASTIC MATERIAL EXPANDED FOR THE CONFORMATION OF PANELS. - Google Patents

Abstract

Procedure for the continuous production of expanded plastic material for the conformation of panels, which consists, during the pouring stage, of introducing at least one reaction component and a mixture of the remaining components at high pressure into a pouring channel (2 ) of a mixing head (1) by means of two injection assemblies (4, 5), said mixture comprising the remaining components polyol mixed with blowing agents and catalysts, said mixture being provided downstream of the high pressure pump (21) spatially separated from the mixing head (1), and during the sustained pouring stage said polyol mixed with blowing agents and catalysts are individually arranged in a recirculation stage, during the recirculation stage the polyol is fed by a first discharge branch (22 ) which is distinct and separated from a second discharge branch (23) in which the mixer (30) is arranged, and during the pouring stage the polyol is introduced into said second discharge branch (23) in order to circulate through the mixer (30), to which at least one conduit (40) is attached to introduce the combinations of blowing agents and catalysts.

Description

Procedure and apparatus for production Continuous expanded plastic material for shaping panels.

The present invention relates to a procedure and to an apparatus for the continuous production of material  expanded plastic for forming panels and the like.

It is known that polyurethane foams expanded are usually obtained by pouring a liquid mixture, called reactive mixture, consisting of reagents, that is, isocyanate and polyol, water, catalysts, etc., and by any blowing agents such as hydrocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, and the like.

In a few seconds, the reaction mixture begins to react, generating heat and carbon dioxide produced by the water-iso- reaction.
cyanate

Carbon dioxide, together with gases generated by evaporation and any blowing agents, due to the heat generated by chemical reactions, it produces the expansion of the reactive mixture to generate the foam.

According to this type of procedure, it has been facilities available for many years that allow the continuous production of low density rigid foam panels for thermal insulation presenting, in cross section, a rectangular shape or if they do not have different shapes; rotting produce said panels in different lengths.

The foam of the lower and upper surfaces of the panels are coupled to substrates of various types, such as for example paper, bituminated paper, wood, metal plate and similar, which form the outer coatings of said panel.

These panels are widely used, in particular, as insulators in the field of building buildings or in the field of industry or refrigeration.

The installations for the manufacture of panels they generally have a series of dosage lines that dose the components in the proportions provided to a head fixed or mobile mixer that feeds the lower substrate of the coating with the mixture produced by said lines, optionally by means of distribution units arranged appropriately.

In another application, the reactive mixtures may apply by depositing in the upper substrate.

The reaction mixture enters a stage of growth and polymerization and is transported, along with the upper and lower coatings, by transport systems and properly arranged mobile containment such as, by example, double conveyor belts, to a cutting machine to cut the panels to the expected length.

A fundamental aspect in obtaining Good quality panels is the way in which the reactive mixture by means of the mixing head on the substrate of the coating.

Therefore, several systems have been proposed depending on the type of panel to be produced and the speeds of production; these systems use, for example, heads Multiple fixtures or a head that performs a reciprocating motion on a guide that is perpendicular to the production axis of the panel.

In the latter case, it is particularly important that the head is light and compact, to allow a easy placement of the injection head between the substrates upper and lower panel before entering the tape double containment.

In any case, however, containment of the weight and dimensions of the heads is a necessity for achieve installation optimization.

In most cases, panel production Thermal insolation requires the use of agents blowers mentioned above and, therefore, said agents blowers are preferably added continuously in the production time, with the advantage of being able to control your dosage according to the physical characteristics of the panel to be occur

The addition can be done directly in the mixing head or premixing, in the exact amount required, by means of static or dynamic mixers, the agent blower with one of the reactive components, for example the polyol, before said component, extracted from the tank of storage, reach the head where the final mixing in order to prepare the reactive mixture that should deposit by pouring into the panel substrate.

The exposure described above for the blowing agent can be extended in any case to other components, catalysts and the like that are involved in the formation of the reactive mixture

The well-known concept is that it is not convenient to make the addition directly to the head of injection, since an immediate consequence would be an increase in dimensions and weight, in addition to an increase in constructive complexity

If high pressure injection heads are used, problems are encountered with regard to the premixing of the various components, which is performed in the low pressure part of the circuit, that is, downstream of the high discharge pump
Pressure.

This aspect produces considerable problems, since it causes an inevitable percolation of the high pump pressure for polyol which, exactly in the case of premixing of low pressure, can produce continuous variations in the proportion Among the various components.

It is also known in the technology of Foamed polyurethane, which precise dosing and control optimum thermostatic of the components fed to the head mixer during the process are extremely important for the obtaining products that have optimal characteristics and constants

For this purpose, for example, it is useful provide, before the pouring stage of the reactive mixture, a recirculation of the components that allows obtain temperature conditions, flow and pressure measurement required, thus avoiding transient disturbances, in the initial periods of the pouring procedure, in which these parameters are not ideal, therefore producing panels that do not have the expected quality characteristics.

In the current state of the art, therefore, the possibility of providing effective recirculation becomes a important factor in ensuring that the physical conditions of components of the reaction mixture remain constant during the Pouring stages and during the recirculation stages.

Document DD 133 642 A discloses a device (4) for mixing gas in a polyol. A circuit of polyol feed (1-3, 6-7) feeds and recirculates the polyol in a mixing device (5) in which is arranged an oscillating cone (8) and around which mixing slots are arranged (10-12). A gas is also fed into one of the mixing slots (10) by a gas conduit (16-19).

The object of the invention is to eliminate the aforementioned drawbacks, providing a procedure for the continuous production of plastic material expanded to form panels and the like that allows perform a high pressure head recirculation stage that allow to avoid altering the proportions between the various components, maintaining the optimum proportions at all times and preventing an incorrect mixture from occurring.

Within this objective, a particular objective of the invention is to provide a method in which it is possible to perform high pressure recirculation despite present a mixing head or a pouring assembly in which only two injection sets are available, thus reducing to a minimum the dimensions and volume of the mixing head.

Another objective of the present injection is in providing an apparatus for the continuous production of material expanded plastic that thanks to its construction characteristics individuals can provide the highest guarantees of reliability and safety in its use.

Another objective of the present invention is to in providing an apparatus that can be easily obtained from of commercially available elements and materials so generalized and that is also competitive from a point of view only commercial.

According to the invention, a process is provided for the continuous production of expanded plastic material for forming panels and the like, as defined in the claims.
attached.

Other features and advantages will be put clearly apparent from the description of a procedure for the continuous production of plastic material expanded for the conformation of panels and the like and of the apparatus to perform the procedure, illustrated with the cooperation of attached drawings, in which:

Figure 1 is a schematic view of the apparatus during the recirculation stage;

Figure 2 is a schematic view of the apparatus during the pouring stage.

Referring to the figures, the apparatus for the continuous production of expanded plastic material for conformation of panels and the like comprises a mixing head, designated in general by reference number 1, which of way per se known internally determines a channel of pour 2 in which a piston can be moved tightly self-cleaning 3, with recirculation slots 4 that are arranged in a first injection assembly 5 and in a second injection set 6.

The piston 3 can perform a movement of translation by means of a piston 7 in order to place the slots 4 in the recirculation position, as shown in the Figure 1, or in a pouring position, in which the piston 3 release the injection assemblies in order to perform mixing and pouring of the foam.

The first injection assembly 5 is connected to a conduit 10 to introduce a mixture of components that may include, for example, polyol mixed with blower reagents, catalysts and
Similar.

For this purpose, a deposit of poliol 20, downstream of which is a high pump pressure 21 that introduces the polyol into a first branch of discharge 22 and a second discharge branch 23, controlled respectively by a first two-way valve 24 and by a second two-way valve 25.

The first branch 22 is connected to the interposition of a first valve of a calibrated track 26, at discharge duct 10 in the immediate vicinity of the head mixer, while in the second discharge branch 23 a mixer 30 is arranged to introduce the components remaining of the mixture.

The second branch 23, downstream of the mixer 30, presents a second valve of a calibrated track 31 connected to the discharge duct 10, which is also in the immediate proximity of the mixing head 1.

At least one of the ducts for introduce the remaining components, such as agents blowers, catalysts, etc., is connected to the mixer 30

The particular example illustrates two ducts 40 in which a respective three-way valve 41 is arranged 41 which connects a product discharge conduit 42 and a conduit of recirculation 43.

The second injection set 6 is connected to a second discharge duct 50 for introduction,  for example, of the isocyanate or in any other component of mix.

In the mixing head are also provided a first recirculation duct 60, arranged in the first injection assembly 5, and a second recirculation duct 61, arranged in the second injection assembly 6.

In practical operation, when the apparatus is in the initial recirculation conditions, the polyol is removed from the storage tank 20 and introduced, by means of the high pressure pump 21, into the discharge leads 22 and
2. 3.

Under recirculation conditions, valve 25 is closed and valve 24 is open, and therefore the polyol circulates through the first branch 22 and, by means of the valve one way or retention 26, is introduced into the mixing head, in which circulating through the slot 4 conveniently arranged is introduces into the first recirculation duct 60, which returns the polyol to the tank 20.

One-way or check valve 31 prevents that the polyol circulates to the mixer 30, thereby isolating to this one and to the corresponding discharge head of the head mixer, which is self-cleaning type.

Obviously, instead of the valves of a via 26 and 31, actuated isolating valves of manual or mechanical way.

In this way, a recirculation is obtained complete that is produced through the head for mixing the polyol only, without blowing agents, catalysts or other components of the reaction mixture, which are recirculated by middle of the three-way valve or equivalent valves, which they provide the deviation of the circulation that arrives from the duct discharge 42 to the corresponding recirculation duct 43 before introduction into the mixer.

It should be added that the device can return the polyol directly to the inlet hole of the high pump pressure 21 instead of directly to the storage tank 20, thus excluding from the recirculation the deposit of storage and any possibility of introducing the agent blower, catalysts and / or other components in the mixture reactive

Obviously, the other component of the reaction, that is isocyanate, is also in the stage of recirculation and is recycled in a conventional manner by means of second discharge duct and the second recirculation duct 61 with the passage through the corresponding slot 4.

In order to pass the recirculation stage to the pouring stage, represented in figure 2, first the mixing head is opened by the action of the piston self-cleaning 3, which is moved by the piston 7, opening of this mode to valve 25 and then closing valve 24, so that the polyol is introduced into the second branch, which sends it to mixer 30.

The three-way valve 41 is also switched, so that the other components of the mixing, such as blowing agents, catalysts and Similar.

The beginning of this sequence, with the opening of the mixer head, interrupts the polyol recirculation stage before the blowing agent, the catalysts or the others components of the reaction mixture that must be premixed with the polyol are introduced into the mixer, making it impossible so said components reach the storage tank 20.

The opening of the valve 25 before the closing of valve 24 provides protection against the danger of overpressures due to the simultaneous closing of the two valves.

At the end of this sequence of operations, take the polyol from storage tank 20 and send it, by middle of the high pressure pump 21 through valve 25 to mixer 30, which also receives the blowing agent, the catalysts and any other components of the reaction mixture through three-way valves 41.

The polyol, after premixing with the agent blower, catalysts or any other components of the Reactive mixture through mixer 30, through the second one-way valve 31, which is also arranged very close to the mixer head, is introduced into the first injection set 5, which injects the mixture into the pouring channel simultaneously with the isocyanate introduced by the other injection set, thus providing the reactive mixture, which leaves the channel of discharge 2.

The one-way valve 26 in practice isolates the first branch 22 of the premixed polyol circulation.

The sequence of operations exposed previously it should be done as quickly as possible, optionally even with a partial overlap of the times of execution of some consecutive operations, to the extent that this is allowed by the components used, following in any case the sequence described, in order to minimize the amount of Reactive mixture that is poured without presenting optimum quality.

At the end of the pouring time, in order to return the installation to the recirculation conditions initial, first three-way valves are switched 41 introduced by blowing agents, catalysts or other components that must be added and simultaneously opens the valve 24 then valve 25 is closed.

Then the mixing head is closed moving the self-cleaning piston 3, which places its grooves 4 in the injection assemblies

This transition to the recirculation stage can optionally be done with a short delay in order to flood discharge duct 10 with pure polyol, which is common for the polyol and the remaining components.

The switching, as a first operation, of the three-way valves 41, and the closure, with an optional delay, of the mixing head, as the final sequence operation, together with the action of the second one-way valve 31, which in the practice isolates the second branch 23 of the mixer head, prevents recirculation to storage tank 20 of amounts of blowing agents, catalysts and other components of the reaction mixture.

The operations outlined above must be done of course as quickly as possible, optionally also with partial overlaps of times of some consecutive operations, to minimize the amount of mixing reactive that is poured, at the end of production, without the required conditions that ensure optimal panel quality produced.

Another important aspect is that the valves of a track 26 and 31 should be mounted as close as possible to the mixing head or directly on said mixing head, minimizing in this way the route shared by the polyol and other components of the mixture, to minimize this time of discharge and the amount of reactive mixture that is poured before the mixing head is closed.

It should also be added that it is possible to provide other structural solutions for the apparatus, such as by example the replacement of the first and second insulators or valves of closing 24 and 25 by a three-way valve, without altering the types of the operating stages that are being carried out.

From the above description it turns out Obviously the invention achieves the purpose and objectives planned and, in particular, highlights the fact that the solution described allows to present a high pressure mixing head with recirculation in it that allows to always obtain a optimal component dosing despite presenting a head mixer with only two injection sets, and allows perform the polyol mixture with the other components of the mixture downstream of the high pressure pump, to always keep the precise values of the percentages of the various components.

The system also has the advantage that during production, if the percentage of the components of the reaction mixture, the effect is immediately evident in the panel being produced; while with the system conventional the transient disturbance would be longer and so so much more finished product would be rejected.

Claims (12)

1. Procedure for continuous production of expanded plastic material for forming panels, which it consists, during the pouring stage, in introducing at least one reaction component and a mixture of the remaining components to high pressure in a pouring channel (2) of a mixing head (1) by means of two injection assemblies (4, 5), said mixing the remaining components polyol mixed with agents blowers and catalysts, said running mixture being provided below the high pressure pump (21) spatially separated from the mixing head (1), and during the sustained pouring stage said  polyol mixed with blowing agents and catalysts are arranged individually in a recirculation stage, during the stage of recirculation the polyol is fed by a first shunt discharge (22) that is different and is separated from a second discharge branch (23) in which the mixer is arranged (30), and during the pouring stage the polyol is introduced into said second discharge branch (23) in order to circulate through of the mixer (30), to which at least one conduit (40) is attached to introduce the combinations of blowing agents and catalysts 2. Method according to claim 1, characterized in that said at least one reaction component is constituted by isocyanate. Method according to one or more of the preceding claims, characterized in that said first discharge branch (22) and said second discharge branch (23) are connected in a supply line (10) of said mixing head (1) and because one-way valves (26, 31) that affect said first branch (22) and second discharge branch (23) are provided. Method according to one or more of the preceding claims, characterized in that said blowing agents and catalysts are recirculated before they are introduced into said mixer (30). 5. Method according to one or more of the preceding claims, characterized in that during the recirculation step, the polyol is returned to the polyol storage tank (20). Method according to one or more of the preceding claims, characterized in that in the transition between the recirculation stage and the pouring stage, the pouring channel (2) is opened in the mixing head (1) and at that time it is opened first, the passage to said second branch (23) to the polyol and then the passage through said first branch (22) is closed, the remaining components of the mixture being introduced after the passage of the polyol to the mixer (30). Method according to one or more of the preceding claims, characterized in that during the transition between the pouring stage and the recirculation stage, the circulation of polyol through said mixer (30) is interrupted once the ducts (40) to introduce the blowing agents and catalysts have been arranged for recirculation. 8. Apparatus for the continuous production of expanded plastic material for forming panels and similar, comprising a mixing head (1) that forms internally a discharge channel (2) in which it can move a self-cleaning piston (3), said piston (3) presenting about recirculation slots (4) that can be arranged in a first injection set (5) and in a second injection set (6) respectively, for said at least a first component and the remaining components of the mixture, the assembly being connected injection (5) for the remaining components of the mixture to a feed line (10) to which a first branch is attached (22) and a second discharge branch (23), said first being  discharge branch (22) different and being separated from said second discharge branch (23), said branches being discharge (22, 23) controlled upstream by means of valve (24, 25) arranged downstream of a high pump pressure (21) whose inlet port is connected to a reservoir supply (20) for polyol, a mixer (30) being provided in said second discharge branch (23) arranged spatially with respect to said mixing head (1) and being connected to at least one conduit (40) for the introduction of blowing agents and catalysts, with a first recirculation duct (60) that is connected to said injection assembly (5) for the return to the tank of Polyol storage (20) of the component. An apparatus according to claim 8, characterized in that it comprises a first one-way valve (26) and a second one-way valve (31) in said first discharge branch (22) and in said second discharge branch (23), said valves being adapted to prevent the return of the material, said first and second discharge leads (22, 23) joining each other in the supply line (10) of said mixing head (1). An apparatus according to one or more of the preceding claims, characterized in that it comprises in said first discharge branch (22) and in said second discharge branch (23), upstream of said mixer (30), a first two-way valve (24) and a second two-way valve (25). 11. Apparatus according to one or more of the preceding claims, characterized in that it comprises, in said at least one conduit (40) for connection to the mixer (30), a three-way valve (4) for recirculation of the corresponding blowing agent and catalyst component 12. Apparatus according to one or more of the preceding claims, characterized in that it comprises, in the discharge of said high-pressure pump (21), a three-way discharge valve that controls said first discharge branch (22) and second branch of download (23).